1. Field of the Invention
The present invention relates to an electronic apparatus such as a portable computer including a heat generating component, and particularly to a structure for improving the cooling performance of the heat generating component.
2. Description of the Related Art
Recently, various portable electric apparatuses represented by notebook-type portable computers, mobile information apparatuses, and the like have been supplied. These electronic apparatuses are equipped with MPUs (Micro Processing Units) for processing multimedia information. In these MPUs, the electric power consumption has steadily increased in accordance with the increase of the processing speed and the number of multiple functions, and the heat generation amount during operation tends to increase rapidly. Heat radiation of the MPU must hence be improved in order to guarantee a stable operation of the MPU. Therefore, various heat-radiation/cooling means such as a heat sink, electric fan, and the like are indispensable.
Conventionally, in a portable computer mounting a MPU having a large heat generation amount, a heat sink is provided on the circuit board equipped with the MPU. The heat sink is thermally connected with the MPU, and cooling air is forcedly sent to the heat sink through the electric fan.
In this conventional cooling method, cooling air serves as a medium which removes heat from the MPU. In many MPUS, therefore, the cooling performance depends on the current strength of cooling air. Meanwhile, portable computers are designed to have a thin compact housing for containing the MPU, a heat sink, and the like. It is therefore difficult to secure an ideal air flow inside the housing, so that the air can be properly exhausted. As a result of this, the lack of proper ventilation of the cooling air leads to a rise in the temperature of the MPU. Consequently, it is impossible to attain a satisfactory cooling performance for the MPU.
A portable computer having an exhaust port whose open area is expandable upon requirements is conventionally known as a measure which solves the above problem. In this portable computer, a part of the peripheral wall of the housing is constructed by a movable wall, and an end of this movable wall is exposed to the exhaust port. The movable wall can shift between a first position in which the exhaust port is defined to be a standard shape and a second position at which the exhaust port is enlarged more than the standard shape. When the movable wall is shifted from the first position to the second position, the open area of the exhaust port is increased so that the cooling air is more easily exhausted.
Therefore, cooling air can easily exit the housing, and accordingly, the amount of cooling air guided to the heat sink increases. Thus, thermal exchange can be efficiently carried out between cooling air and the heat sink, so that the cooling performance of the MPU can be improved.
However, according to conventional portable computers, an increase of the flow amount is very small in comparison with the heat generation amount, although the flow amount of cooling air guided to the heat sink is increased. In addition, the heat radiation area of the heat sink which contributes to heat radiation does not change but is maintained constantly. Therefore, a remarkable improvement of the cooling performance of the MPU cannot be expected even if the flow amount of cooling are guided to the heat sink increases.
MPUs for use in portable computers are expected to attain higher speeds and perform more functions in the near future. Hence, the heat generation amount of the MPU is assumed to increase remarkably. Therefore, it cannot be said that the conventional cooling method of merely expanding the open area of the exhaust port sufficiently respond to the increase of the heat generation amount of the MPU. Consequently, it is considered that the cooling performance of the MPU will be insufficient or be limited.
The present invention has an object of providing an electronic apparatus capable of greatly improving the heat radiation performance of a heat sink and of maintaining a proper operating environment temperature of a heat generating component.
To achieve the above object, an electronic apparatus according to the first aspect of the present invention comprises: a housing having a ventilation port and being able to be displaced between a first usage form in which the ventilation port is set in a standard opening shape, and a second usage form in which the ventilation port is enlarged to be larger than the standard opening shape; a heat generating component contained in the housing; and a heat sink thermally connected with the heat generating component and contained in the housing so as to face the ventilation port, the heat sink having a plurality of heat radiation fins whose heat radiation range expands when the housing is displaced from the first usage form to the second usage form and is reduced when the housing is displaced from the second usage form to the first usage form.
In this structure, heat from the heat generating component is transferred to the heat sink by thermal conduction, and is diffused in the housing through the surface of the heat sink and the heat radiation fins. When the housing of the electronic apparatus is displaced from the first usage form to the second usage form, the heat radiation fins are deformed so as to enlarge their heat radiation range. In this manner, the contact area between the heat radiation fins and air increases so that the heat from the heat generating component can be efficiently radiated.
Therefore, when the heat generation amount of the heat generating component increases, the heat radiation performance of the heat sink can be improved so as to comply with increase of the heat generation amount, by displacing the housing. Accordingly, it is possible to maintain a sufficient cooling performance of the heat generating component even if the installation space for the heat sink is limited due to downsizing of the housing.
To achieve the above object, an electronic apparatus according to the second aspect of the present invention comprises: a housing including a heat generating component; and a heat sink contained in the housing for receiving heat from the heat generating component. The heat sink includes a plurality of heat radiation fins made of shape-memory alloy, the heat radiation fins stand up with an interval maintained between each other when the heat sink receives heat from the heat generating component and a temperature of the heat radiation fins reaches a shape-memory range, and the heat radiation fins are elastically deformed when the temperature of the heat radiation fins exits the shape-memory range.
In this structure, heat from the heat generating component is transferred to the heat sink by thermal conduction, and is diffused in the housing 4 through the surface of the heat sink and the heat radiation fins. In a stage before the temperature of the heat radiation fins reaches a shape-memory temperature, the heat radiation fins are in a flexible state and can be deformed into a free shape. Therefore, the heat radiation fins are deformed into a shape in which their heat radiation range is reduced while the heat generation amount of the heat generating component is small.
When the temperature of the heat radiation fins reaches the shape-memory temperature, these heat radiation fins stand up with an interval maintained between each other due to the shape-memory effect, so that the heat radiation range expands. Accordingly, adjacent heat radiation fins move apart from each other, so that gaps which allows air to pass are formed between the heat radiation fins each other. As a result of this, the contact area between the heat radiation fins and air increases so that the heat transferred to the heat radiation fins from the heat generating component can be efficiently radiated. Therefore, the heat radiation performance of the heat sink can be improved so as to comply with an increase of the heat generation amount of the heat generating component, by utilizing the shape-memory effect of the heat radiation fins.
To achieve the above object, an electronic apparatus according to the third aspect of the present invention comprises: a housing including a heat generating component and having an exhaust port; a movable wall associated with the housing, forming part of the exhaust port, the movable wall being supported on the housing such that the movable wall is movable between a first position at which the exhaust port is defined by a standard opening shape and a second position at which the exhaust port is expanded to be larger than the standard opening shape; a heat sink thermally connected with the heat generating component and contained in the housing so as to face the exhaust port, the heat sink having a plurality of heat radiation fins whose heat radiation range expands when the movable wall is moved to the second position and is reduced when the movable wall is moved to the first position; and a fan contained in the housing, for blowing cooling air toward the heat sink such that the cooling air passes between the heat radiation fins and is exhausted to the outside of the housing through the exhaust port.
In this structure, heat from the heat generating component is transferred to the heat sink by thermal conduction, and is diffused in the housing through the surface of the heat sink and the heat radiation fins. The heat sink receives cooling air sent from the fan, so that the heat from the heat generating component transferred to the heat sink and the heat radiation fins is removed by the cooling air. The cooling air warmed up by thermal exchange with the heat sink is exhausted to the outside of the housing.
When the movable wall of the housing is moved from the first position to the second position, the opening shape of the exhaust port is expanded so that the exhaust resistance of the cooling air is reduced. In this manner, cooling air tends to come out from the inside of the housing, so that the flow amount of the cooling air increases. In addition, the heat radiation fins of the heat sink are deformed so as to enlarge their heat radiation range, following the expansion of the opening shape of the exhaust port. In this manner, the contact area between the heat radiation fins and air increases.
As a result of this, cooling air can be actively guided as much as possible to the heat radiation fins whose heat radiation range is expanded. The heat transferred to these heat radiation fins from the heat generating component can be efficiently radiated to the outside of the housing. Therefore, the heat radiation performance of the heat sink can be improved in compliance with increase of the heat generation amount of the heat generating component, so that it is possible to maintain the cooling performance of the heat generating component.
To achieve the above object, an electronic apparatus according to the fourth aspect of the present invention comprises: a housing including a heat generating component; and a heat sink contained in the housing, thermally connected with the heat generating component, and having a plurality of heat radiation fins whose heat radiation range changes in accordance with a heat generation amount of the heat generating component.
In this structure, heat from the heat generating component is transferred to the heat sink by thermal conduction, and is diffused in the housing through the surface of the heat sink and the heat radiation fins. Since the heat radiation range of the heat radiation fins changes in accordance with the heat generation amount of the heat generating component, it is possible to improve the heat radiation performance of the heat sink in compliance with increase of the heat generation amount of the heat generating component. Accordingly, it is possible to improve the cooling performance of the heat generating component even if the installation space for the heat sink is limited due to downsizing of the housing.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.